1. Field of the Invention
The invention relates to window and wall washing devices for the exterior window and wall surfaces of high-rise buildings. More particularly the present invention concerns a unit which in operation is spaced apart from the exterior surfaces of the walls and windows of a high-rise building and which is provided with a perimeter air curtain to retard the egress of washing liquids from the space between the unit and the exterior window and wall surfaces.
2. Description of the Prior Art
High-rise buildings having fixed glazing are relatively new. Prior to the past decade, most, if not all, high-rise buildings employed movable glazing which permitted window cleaning to be conducted from the inside of the buildings. Within the past decade, fixed glazing has become popular and has created a need for other methods of washing the outside surfaces of the glazing. There is also a need for washing the outside surface of the infill panels between the fixed glazing in typical high-rise buildings. Numerous devices have been proposed for accomplishing the window washing by means of unmanned units which traverse the exterior surfaces of the buildings; some units are self-propelled; others are raised and lowered by means of cables connected to the top of the building. Such units have included means for delivering cleaning liquid such as water or detergent solutions, and have included means for scrubbing the window wall such as brushes and/or sponges and have included means for retarding the egrees of cleaning liquid in the form of squeegee blades. Such devices are shown in U.S. Pat. Nos. 3,292,193 (LITTEN, Dec. 20, 1966); 3,298,052 (NOLFE, January, 1967); 3,425,082 (HETMAN, Feb. 4, 1969); 3,344,454 (MIKALSON, Oct. 3, 1967); 3,497,902 (HARTIGAN, Mar. 3, 1970). To date such devices have experienced only limited commercial acceptance.
In some instances because of discontinuities in the building exterior surface unmanned wall-washing units have become immobilized at locations many floors above street level requiring hazardous rescue operations in high winds by workmen on scaffolds or ropes on the exterior of the buildings.